The present invention concerns a system for controlling the operation of a motor vehicle diesel engine associated with depollution means comprising an oxidation catalyst and arranged in an exhaust line of this engine, this catalyst having at least one non-initialized operating state and one initialized operating state, and this engine being also associated with means for supplying fuel to the cylinders thereof according to least one injection during their expansion phase.
It is constant that the combustion of fuel in a Diesel engine causes an emission of pollutants, such as, for example, nitrogen oxide (NOx) and sulfur (Sox) particles. In order to reduce these emissions, in a standard manner, the engine is associated with an exhaust line equipped with depollution means comprising a particle filter (PF) or a NOx trap, for example, intended to store such particles.
Since the depollution means do not have an unlimited storage capacity, it is necessary to regenerate them periodically and/or regularly. To this effect, the exhaust line comprises, upstream of the depollution means, an oxidation catalyst adapted to generate an exotherm upstream of these depollution means, which increases their internal temperature and thus assists their regeneration.
In a standard manner, a diesel engine is associated with means for supplying fuel to its cylinders, adapted to supply the cylinders according to multiple fuel injections during their expansion phase, or “post-injections,” or else to shift the main injection toward the expansion phase. The fuel thus injected during the expansion phase of the cylinders is unburned and is delivered to the catalyst for its oxidation and for the production of the exotherm.
In order for the fuel supplied to the catalyst to be oxidized in a satisfactory manner, the catalyst must have a sufficient internal temperature, i.e., an “initialized” operating state. To bring it into such a state, the means for supplying fuel to the cylinders are adapted to supply the cylinders according to a predetermined catalyst initialization value.
In its initialized state, the catalyst then generates an exotherm in an efficient manner by oxidizing the fuel from the fuel injection supplied by the supply means adjusted to a predetermined initialized state-maintaining injection value.
Systems for controlling the operation of a diesel engine of the type mentioned above are known in the state of the art, which are adapted to assist the regeneration of the PF by evaluating the operating state of the catalyst and by controlling the commutation between post-injection values on the basis of this evaluation.
For example, the patent FR 2 804 176 describes such a control system which comprises first and second temperature sensors arranged in the exhaust line upstream and downstream of the catalyst, respectively. The measurements from these sensors are supplied to means for controlling the supply means adapted to estimate the state of the catalyst as a function, of both temperature measurements upstream and downstream of the catalyst and to control the commutations between post-injection values as a function of the estimated operating state of the catalyst.